The tightest knot ever is also one of the tiniest. Made of strings of molecules braided together, the knot is only 20 nanometres long, and its properties are as yet unknown. But researchers hope that these tied-up molecules could lead to lighter body armour or more flexible surgical sutures.
Molecular knots like this are probably more analogous with the knots in mathematics, which are closed loops twisted into different shapes, than with the knots in your phone charger鈥檚 cord.
The first molecular knot 鈥� one of the most mathematically simple kinds called a trefoil knot 鈥� was tied in 1989. From then until 2011, chemists only knew how to coax molecules into that one type of knot.
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鈥淭here are over 6 million different sorts of knots known to mathematicians, and chemists had been able to make just one, which was pretty pathetic,鈥� says at the University of Manchester, UK.
Gimme five
In 2011, Leigh was part of the first team to create a synthetic pentafoil knot. Whereas the strands of a trefoil knot cross over one another three times, those in a pentafoil knot have five crossings.
Now Leigh and his team have made a knot with eight crossings, making it the most complex molecular knot ever tied.
Leigh and his team used a precise mix of ions under controlled conditions to braid the strands of molecules together in a process called self-assembly. The final knot is made up of 192 atoms and includes chlorine, hydrogen and nitrogen, among other elements.
鈥淭he strands that we鈥檙e knotting are so small that you can鈥檛 grab the ends and mechanically tie them like you would a shoelace,鈥� says Leigh. 鈥淯nlike tying your shoelaces, where you do them one at a time, with self-assembly we can tie many billions of molecular knots at the same time.鈥�
Bulletproof vests
鈥淭his is a synthetic masterpiece, formed in a very simple and extraordinarily elegant manner,鈥� says at Trinity College Dublin, Ireland.
The method may enable chemists to synthesise more types of knotted molecules in large batches.
鈥淚t is quite likely that these knotted molecules will show properties different from un-knotted ones, but nobody鈥檚 done the research yet to show what those might be,鈥� says at the University of Cambridge.
Leigh says the practical applications of knotted molecules will probably only be discovered when chemists try to weave them together, a process that is similar to knotting. He imagines these woven materials could be used to make anything from lighter bulletproof vests to more flexible surgical sutures.
鈥淚n our everyday world, we know the benefits of weaving fabrics,鈥� he says. 鈥淵ou get materials that can stretch in different directions, hold their shape, they鈥檙e light and strong and flexible 鈥� hopefully we can use the same principles and get related effects at the molecular level.鈥�
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